* {
    padding: 0;
    margin: 0;
}

#app {
    width: 100%;
    height: 200px;
    border-bottom: 2px red solid;
}

#app ul {
    display: flex;
}

#app li {
    list-style: none;
    width: 300px;
    height: 200px;
    line-height: 200px;
    text-align: center;
    background-color: white;
}

#app li a {
    text-decoration: none;
    color: black;
    display: block;
    width: 100%;
    height: 200px;
}

.active {
    background-color: red;
}